U.S. death row inmate Christa Pike has returned to prison a week after she was hospitalised following her survival of two doses of pentobarbital, a drug used in state executions.

Following a tumultuous week of a botched execution and a critical health condition, Ms Pike, 50, returned to the Tennessee women’s prison on Saturday.

She returned to the Deborah K. Johnson Rehabilitation Centre, where she spent the last 30 years for killing her classmate, Colleen Slemmer, in the woods in 1995.

Her lawyers have pushed for Ms Pike to spend the rest of her life in prison, arguing her small veins would make death by drugs difficult to achieve.

Tennessee prison chief Frank Strada, who oversaw the failed execution, announced his resignation effective October ending following a backlash from citizens over the incident.

Judge I’Ashea Myles ordered Tennessee prison officials to preserve a wide range of evidence, including syringes and IV lines used in last week’s botched execution.

The Davidson County Chancery Court in Nashville directed the officials to preserve the logbook, medical waste and everything that was used in the execution room on September 30.  

“Anything in the actual room needs to be preserved and maintained,” the judge said earlier this week.

It is unclear whether the state will immediately attempt another execution or wait till next year before trying again.